1. Field of the Invention
The present invention relates to a cleaning apparatus for a copying machine which employs a resilient roller. More particularly, tne invention pertains to a cleaning apparatus in which a resilient roller is rotated in such a manner as to be in resilient contact with the surface of a photosensitive member, thereby removing toner remaining on the surface of the photosensitive member, and also removing any charging product formed thereon as the result of charging, and any other foreign substances, such as dust, which may be attached to the photosensitive member surface.
2. Description of the Prior Art
U.S. Pat. Nos. 3,838,472, 3,634,077 and U.S. Pat. No. 3,656,200 all disclose electrophotographic copying machines having a cleaning roller apparatus to remove toner which remains on the surface of a photosensitive member after an image transfer operation. However, the cleaning roller driving mechanism of the present invention is not disclosed in the known prior art.
Referring now to FIG. 1, there is shown schematically a cross-section view of a conventional cleaning apparatus which employs a resilient roller and which is applied to an electrophotographic copying machine. The copying machine operates as follows: The surface of a cylindrical photosensitive member 1, which is rotated in the direction of the arrow A in FIG. 1, is first uniformly charged by an electrostatic charger 2 which is disposed at the periphery of the photosensitive member 1. Then, a light image 7 is projected onto the charged surface of the photosensitive member 1, whereby an electrostatic latent image, which corresponds to the light image 7, is formed on the surface of the photosensitive member 1. As the photosensitive member 1 continues to rotate, the latent image passes by a developer 3 where it is transformed into a visible image of toner. This toner image is the transferred to a transfer medium, such as paper 4, which is fed to a transfer section having a transfer electrode 5. The transfer medium is then conveyed to a fixing section (not shown). During the above-described operation, any toner which has not become transferred to the paper 4 or other transfer medium at the transfer section consequently remains on the surface of the photosensitive member 1, together with other foreign substances. This remaining toner and the other foreign substances are then carried by the photosensitive member 1 past a cleaning apparatus 6 where they are removed from the surface of the photosensitive member. Thus, before reaching the charging section, the surface of the photosensitive member 1 is restored to a state wherein a subsequent copying operation can be effected.
The cleaning apparatus 6 in the copying machine of the type described above generally employs a resilient roller 8 which is disposed inside the cleaning apparatus 6. The arrangement of the cleaning apparatus 6 will now be described in more detail with reference to the enlarged fragmentary cross section view of FIG. 2.
As will be clear from FIG. 2, the cleaning apparatus 6 includes an elongated casing 6b which extends parallel to and in close proximity with the photosensitive member 1. A cleaning blade 6a is mounted on an upper part of the casing 6b. The cleaning blade 6a has one edge thereof brought into resilient contact with the surface of the photosensitive member 1 so as to scrape away, in well known manner, any remaining toner which clings to the surface of the photosensitive member 1 and is conveyed together therewith.
A resilient cleaning roller 8 is disposed in the casing 6b, on the upstream side of the cleaning blade 6a (in terms of the direction of rotation of the photosensitive member 1, which turns in the direction of the arrow A in FIG. 2). The cleaning roller 8 comprises an inner layer 8b of relatively low hardness silicone sponge material and an outer layer 8a of a relatively high hardness stable silicone rubber. The outer layer 8a of the cleaning roller 8 is maintained in resilient contact with the surface of the photosensitive member 1. The cleaning roller 8 rotates in the direction of the arrow B at a relative velocity with respect to the surface of the photosensitive member 1 and brushes against the surface of the photosensitive member in such a manner as to remove the remaining toner, paper dust, corona product, and so forth, from the surface of the photosensitive member 1.
The remaining toner and other substances which have thus been removed from the photosensitive member 1 by the cleaning roller 8 and which have been scraped off from the photosensitive member 1 by the cleaning blade 6a, are carried around with rotation of the cleaning roller 8 and are scraped off from the surface of the roller 8 by means of a scraper 10. Such toner and other substances are thereby deposited in a storage portion of the casing 6b before being discharged to the outside of the casing 6b by means of a screw conveyor 9.
In the above described cleaning apparatus 6, the resilient contact pressure applied to the surface of the photosensitive member 1 by the resilient cleaning roller 8 is calculated in terms of the nip therebetween. An excessively large nip pressure undesirably makes it easy for the surface of the photosensitive member 1 to become cracked or flawed. On the other hand, an excessively small nip pressure unfavorably reduces the effectiveness of the cleaning roller 8 in removing charging products from the surface of the photosensitive member. Accordingly, it has heretofore been necessary to finely adjust both the width and the balance of the nip in the longitudinal direction of the photosensitive member 1 and the cleaning roller 8 during the rotation of both members. Moreover, as the roller 8 becomes worn, it is necessary as a matter of course to effect an additional fine adjustment by an amount corresponding to the degree of wear. These adjustments have previously been carried out by moving the position of the cleaning roller 8 with respect to the photosensitive member 1 while measuring the distance between their respective centers. Accordingly, in this method, the nip adjustment is effected by properly adjusting the distance between the respective centers of the photosensitive member 1 and the cleaning roller 8; and in such case the nip width undergoes a large change with respect to any given change in the distance between the respective centers of the photosensitive member 1 and the cleaning roller 8. This situation requires a very delicate adjustment (e.g., the nip width changes by 0.5 to 1 millimeters (mm) when the distance between centers is changed by 60 microns (.mu.)). Variations in the nip width involve adverse effects as described above. That is, an excessively small nip width reduces the effectiveness of the cleaning roller 8 in removing charging products, which is a primary object of the provision of the cleaning roller 8; while an excessively large nip width causes the photosensitive member 1 to be easily cracked.
One conventional method of adjusting the nip width, as illustrated in FIG. 3, involves pressing the cleaning roller against the surface of the photosensitive member 1 by means of springs 20. With this method, however, the balance between the two ends of the cleaning roller 8 is easily destroyed due to the pressing force applied to the cleaning roller 8 by the driving gear which rotates the cleaning roller. Should there be any imbalance in the pressing force at the two ends of the cleaning roller 8, such condition will produce a variation in the nip along the surface of the photosensitive member 1 in its longitudinal direction.